There is a widespread concern for climate change characterized by environmental warming. Although the trend has been attributed to a number of causes, the greatest attention has been directed to the release of greenhouse gases. Chief among these gases is carbon dioxide because of its ability to trap heat.
With the growing concern about an increased concentration of carbon dioxide in the atmosphere, there is a movement to reduce the emissions of this greenhouse gas. The effort is being waged under the banner of “Carbon Capture and Storage,” or “Carbon Capture and Sequester,” also known as “CCS” for short. Success in this endeavor requires either the avoidance of carbon dioxide generation in the first place or the recovery of this gas from industrial processes. The most notable example is electric power generation.
Technology presently exists for the recovery of carbon dioxide from exhaust gas, but to date the application of this know-how has been limited. The primary target for this technology is the combustion of fossil fuels including coal, oil and natural gas. All three fuels are of concern, but coal has received the brunt of criticism because it is one hundred percent carbon and also because it poses other environmental risks due to such impurities as sulfur and mercury.
Focusing on the recovery of carbon dioxide while ignoring questions of storage and disposal, two approaches for carbon capture have been proposed. Carbon dioxide can either be recovered by adsorption on a solid sorbent or dissolved in an aqueous solution. In the first instance, such solid materials as activated carbon, Small zeolites, and metal organic frameworks are used to bind the carbon dioxide. Adsorption, however presents certain challenges. Care must be taken to avoid attrition of the solid sorbent. Additionally, significant energy is required to regenerate the sorbent. Either pressure swings or the heating of the sorbent to release the adsorbed gas is required.
A second method of carbon capture depends on the absorption of carbon dioxide in a solvent. In this application, an aqueous solution of an amine is most commonly used. The amine of choice is monoethanolamine. While the solvent is efficient in scrubbing flue gases, its regeneration presents a problem. Relatively high temperatures are required to strip carbon dioxide from pregnant solutions.
The conventional or “prior art” process is disclosed in WO 2015/053619 A1. Flue gas containing carbon dioxide is introduced to the bottom of a counter current scrubbing column while vent gas, mostly nitrogen, is removed overhead. Solvent with dissolved ammonia and salt is circulated between the scrubber and stripper. Inevitably, some ammonia escapes into the vent, thus rendering the process less efficient.
In summary, the available technology for carbon capture has a number of drawbacks. These handicaps are most serious in large scale facilities. The result is poor economics, which has held back the exploitation of current methodology.
The future prospect for carbon capture is very much dependent on the introduction of process improvements. The need for such advancements is all too apparent. Therefore, it is an object of the present invention to fulfill such aspirations. These and other objects and goals will become apparent from the following description and the drawing included therewith.